I love Geekzone. This discussion would have become troll and fanboy city in most places around the internet. Very good advice going on here, well done everyone!

I think everyone here has covered things well, so don't feel particularly pressured to add my 2c.

I will say that the GPU discussion is a bit esoteric based on what the OP said their use would look like, probably not adding a lot of value to the OP's decision making process, and more likely needlessly confusing it. For his use any of these phones should be just fine.

Reading between the lines it looks like the OP will need a reasonable amount of storage, in which case the SGSII probably becomes the front runner with a 32GB card. 64GB cards do work, as discussed, but their price is prohibitive right now - depending on how long you intend to own the phone for that does increase the future proofing, since they will be cheaper later, and 128GB cards should also work in the fullness of time. The Galaxy SII is confirmed to be getting the latest version of the Android OS (Ice Cream Sandwich), so again reasonable future proofing in that regard. 

EDIT: Oh, as someone mentioned earlier - my blog will have indepth reviews on the Nexus, Galaxy Note, and Motorola Razr in the month of November, and you can check out my review on the Galaxy S II at Clove also. At the risk of sounding immodest I think it is one of the best reviews on the internet, mostly for the fact that its a proper users review unlike most of what is out there (other excellent reviews would be the Anandtech one, and GSMarena which also has a review of the iPhone 4 for the OP to compare with).
 

ASIDE: I've seen that drop test posted loads of places, but hadn't viewed it until now - EEEK! I've dropped by S2 a few times onto lino and suffered no damage whatsoever, so it doesn't surprise me that much (I hope people who have watched the video are getting the distinction I draw between build materials and build quality now!).